Underground pipeline and cable detector and process

• US 4,600,356 A
• Filed: 01/27/1984
• Issued: 07/15/1986
• Est. Priority Date: 01/27/1984
• Status: Expired due to Fees

• Current Assignee: Gas Research Institute (GTI Energy)
• Original Assignee: Gas Research Institute (GTI Energy)
• Inventors: Bridges, Jack E., Sutkowski, Robert J., Hofer, Kenneth E. Jr.
• Primary Examiner(s): Dolinar, Andrew M.
• Application Number:
  US06/574,568
• Time in Patent Office: 900 Days
• Field of Search: 414/699, 414/694, 37/DIG. 1, 37/DIG. 19, 324/329, 324/326, 324/67, 172/6
• US Class Current: 414/694
• CPC Class Codes: E02F 9/245 for preventing damage to underground objects during excavation, e.g. indicating buried pipes or the like detection of pipes in the ground F16L1/11

Abstract

An apparatus and process combining an excavation apparatus with a fully contained underground elongated conductive object detector capable of selectively detecting underground objects such as water pipes and electrical cables. The combination of this invention may be advantageously used in trenching to prevent damage to underground water pipes and electrical cables by detecting their presence before the digging implement damages them. An audible or visual signal may be activated and/or the excavation apparatus may be automatically shut down upon detection of an underground pipe or cable a few feet below the excavation. The detector may be incorporated in the digging shovel of a backhoe or maintained in position adjacent the digging implement by a boom extending from the excavation apparatus. Simple and sturdy time gated electronics is advantageously used to differentiate underground pipes and cables from other underground metal debris and to provide range and direction information.

Claims

1. An apparatus capable of making excavation in the ground in combination with a fully contained underground elongated conductive object detector comprising:

a transmit and receive means capable of locating an underground elongated conductive object in the proximity of said excavation mounted in a digging implement comprising a metal bucket, said transmit and receive means installed on the inside of the digging face of said bucket, said digging face having a multiplicity of through slots covered with non-conducting material in the vicinity of said transmit and receive means, and the edges of a heavy metal entry face frame having multiple interruption slots reducing the time value decay constants of induced eddy currents;

means for providing an electric pulse signal to said transmit means, said transmit means capable of transmitting a pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

said receive means capable of receiving eddy currents induced by said underground conductive object contacted by said pulsed magnetic transmit field and transmitting an electrical signal proportionate to said eddy currents;

said pulsed magnetic transmit field having decay times substantially less than said eddy current decay time;

means for electronically processing said eddy current electrical signal to determine the presence of said underground conductive object.

2. An apparatus capable of making excavation in the ground in combination with a fully contained underground elongated conductive object detector comprising:

a transmit and receive means capable of locating an underground elongated conductive object in the proximity of said excavation mounted in a digging implement comprising a non-conductive polymeric bucket portion, said transmit and receive means installed on the inside of the digging face of said bucket body;

means for providing an electric pulse signal to said transmit means, said transmit means capable of transmitting a pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

said receive means capable of receiving eddy currents induced by said underground conductive object contacted by said pulsed magnetic transmit field and transmitting an electrical signal proportionate to said eddy currents;

said pulsed magnetic transmit field having decay times substantially less than said eddy current decay time;

means for electronically processing said eddy current electrical signal to determine the presence of said underground conductive object.

3. An apparatus according to claim 2 wherein said bucket body has a metallic frame around its open entry face and the edges of said frame has multiple interruption slots reducing the time constant decay values of induced eddy currents.

4. An apparatus according to claim 2 wherein said bucket portion is provided with a metal entry face frame interrupted by an insulator to decrease interference with said transmit and receive means installed therein.

5. A process for detection of underground elongated conductive objects during excavation with an excavation apparatus having a fully contained underground elongated conductive object detector, said process comprising the sequential steps:

providing an electrical pulse signal, powered by a power source of said excavation apparatus, to a transmit coil mounted in a digging implement comprising a metal bucket having said transmit and receive means installed on the inside of the digging face of said bucket, said digging face having a multiplicity of through slots covered with non-conducting material in the vicinity of said transmit and receive means, the edges of a heavy metal entry face frame having multiple interruption slots reducing the time constant decay values of induced eddy currents, said transmit coil forming a pulsed magnetic transmit field;

transmitting said pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

receiving in a receive coil mounted in said digging implement pulsed eddy currents induced by said underground elongated conductive object contacted by said pulsed magnetic field;

converting said pulsed eddy currents into an electrical pulse signal proportionate to said eddy currents, said eddy currents having a decay time at least five times as long as the decay time of said pulsed magnetic transmit field;

electronically processing said eddy current electrical signal to determine the presence of said underground elongated conductive object.

6. A process for detection of underground elongated conductive objects during excavation with an excavation apparatus having a fully contained underground elongated conductive object detector, said process comprising the sequential steps:

providing an electrical pulse signal, powered a power source of said excavation apparatus, to a transmit coil mounted in a digging implement comprising a non-conductive polymeric bucket body portion having said transmit and receive means installed on the inside of the digging face of said bucket body, said transmit coil forming a pulsed magnetic transmit field;

transmitting said pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

receiving in a receive coil mounted in said movable appendage pulsed eddy currents induced by said underground elongated conductive object contacted by said pulsed magnetic field;

converting said pulsed eddy currents to an electrical pulse signal proportionate to said eddy currents, said eddy currents having a decay time at least five times as long as the decay time of said pulsed magnetic transmit field;

electronically processing said eddy current electrical signal to determine the presence of said underground elongated conductive object.

7. The process of claim 6 wherein said bucket body has a metallic frame around its open entry face and the edges of said frame has multiple interruption slots reducing the time constant decay values of induced eddy currents.

8. The process according to claim 6 wherein said bucket portion is provided with a metal entry face frame interrupted by an insulator to decrease interference with said transmit and receive means installed therein.

9. An apparatus capable of making excavation in the ground in combination with a fully contained underground elongated conductive object detector comprising:

a transmit and receive means capable of locating an underground elongated conductive object in the proximity of said excavation mounted in a digging implement comprising a fiber-reinforced-plastic bucket with a metal frame entry face, said transmit and receive means installed on the inside of the digging face of said bucket, and said metal frame entry face interrupted by an insulator to decrease interference with said transmit and receive means;

means for providing an electric pulse signal to said transmit means, said transmit means capable of transmitting a pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

said receive means capable of receiving eddy currents induced by said underground conductive object contacted by said pulsed magnetic transmit field and transmitting an electrical signal proportionate to said eddy currents;

said pulsed magnetic transmit field having decay time substantially less than said eddy current decay time;

means for electronically processing said eddy current electrical signal to determine the presence of said underground conductive object.

10. A process for detection of underground elongated conductive objects during excavation with an excavation apparatus having a fully contained underground elongated conductive object detector, said process comprising the sequential steps:

providing an electrical pulse signal, powered by a power source of said excavation apparatus, to a transmit coil mounted in a digging implement comprising a fiber-reinforced-plastic bucket body portion with a metal frame entry face having said transmit and receive means installed on the inside of the digging face of said bucket body, said transmit coil forming a pulsed magnetic transmit field;

transmitting said pulsed magnetic transmit field outwardly through the ground in the direction of said excavation;

receiving in a receive coil mounted in said digging implement pulsed eddy currents induced by said underground elongated conductive object contacted by said pulsed magnetic field;

decreasing interference of said metal frame entry face with said transmit and receive means by providing an insulator interrupting said metal frame entry face;

converting said pulsed eddy currents to an electrical pulse signal proportionate to said eddy currents, said eddy currents having a decay time at least five times as long as the decay time of said pulsed magnetic transmit field;

electronically processing said eddy current electrical signal to determine the presence of said underground elongated conductive object.